I remember scrolling through YouTube's recommendations, stumbling across a video on osu!mania (I think it was
Staiain's Galaxy Collapse video). It was one of those "why not" moments, so I clicked on it, only to find myself so confused as to what was happening on the screen and how could a human being react that fast and accurately. I may have seen the game before, but this was my first exposure that I know of and remember.
Right after I watched the video, I looked up the game and downloaded it, because I was somehow so determined to get good at it. And, after a few hiccups and several attempts to play standard, to this very day, I'm still playing, and likely won't stop anytime soon.